Measurement of the gas content of metals by mass spectroscopy



United States Patent 3,546,448 RAILWAY SIGNALING SYSTEM William M. Pelino, Richmond, Va., assignor to Railtron Corporation, Richmond, Va. Filed Sept. 5, 1968, Ser. No. 757,738 Int. Cl. B61k 13/00 US. Cl. 246-246 13 Claims ABSTRACT OF THE DISCLOSURE A railway signaling system including electromagnetic transducer means mounted adjacent a railroad track and adapted to provide no response to the vibrations attendant the passage of a normal vehicle but providing an electrical output in response to an impact by an improperly protruding vehicle member.

The invention pertains generally to railway signaling systems, and more particularly to railway signaling systems of the type utilized for monitoring the operating conditions of railway vehicles, such monitoring in accord ance with this invention being adapted to the sensing of improperly protruding vehicle members upon passage of a train or the like past a sensing station at railside. A specific illustration of an application of this invention in the railway art is the detection of equipment improperly depending from a railroad car, and means for detecting such faults are commonly referred to as dragging equipment detectors.

The prior art has known many different types of socalled dragging equipment detectors, and one common form includes pivotally mounted paddles or similar members positioned on a railroad track at a location over which a passing trail will travel. The paddles extend upwardly from their pivotal mounts and are of such dimensions as to permit passage of a normal train vehicle thereover with no contact between the detector and the vehicle, while a vehicle with improperly depending or dragging equipment causes an indication or alarm by virtue of the engagement of the paddles as the vehicle passes thereover. This pivotal movement is translated by suitable mechanical means into, for example, a visual signal, indicating to railway personnel that the train is dragging equipment.

While such dragging equipment detectors of the prior art are satisfactory for some purposes, they are subject to malfunctions under certain operating conditions which render them all but useless. For example, in cold weather the pivotal paddles may freeze in position, resulting in a failure to exercise the required pivotal movement (and, sometimes, breakage of the paddles) upon being struck by a piece of dragging equipment. Also, a heavy blanket of snow settled around the prior art detectors sometimes inhibits such movement of the paddles. Further, the detectors of the prior art are an easy prey to vandalism.

The prior art has also provided other systems for monitoring a passing train for out-of-position equipment, whether such equipment is dragging equipment, is otherwise protruding or is in some other manner not properly positioned relative to the other parts of the train or relative to the rails over which the train passes. However, these other prior art systems are characterized by structural features similar to those described above, and are accordingly subject to the same or similar limitations.

It is therefore an object of this invention to provide a system for monitoring passing railway vehicles for out-ofposition equipment, without the limitations and malfunctions characteristic of the prior art systems.

More specifically, it is an object of this invention to provide an improved dragging equipment detector.

Further, it is an object of the present invention to provide an improved equipment for detecting loose flanged wheels on a railway vehicle.

A still further object of the invention is to provide an improved detector for railway vehicle wheels having worn or cupped treads.

In accordance with the present invention, these and other objects are achieved by means of a railway signaling system having electromagnetic transducer means mounted adjacent a railroad track in a position relative to the rails and vehicles passing thereover such that normal vehicles may pass without contact between the vehicle members and the transducer means or the mounting means therefor. However, upon the passage of railway vehicles having members thereof out-of-place and protruding beyond a position of normal clearance, such protruding members will strike the transducer assembly, and the impact results in an electrical output from the transducers.

The transducers in the signaling system of this invention are preferably mounted within and protected by metallic strike plates or the like, and it is the strike plate which bears the impact of the protruding vehicle equipment. Upon such impact, the vibrations set up in the strike plate are transferred to the transducers as a mechanical input thereto, such input being characterized by a sharp sound having a steep wave front.

Since the vibrations attendant the passage of railway vehicles is characteristically a relatively low-frequency rumble, in sharp contrast to the higher audio frequency vibrations associated with the impact against the strike plates (which are preferably of heavy steel construction), the present invention renders it possible to distinguish therebetween so as to provide an output indication as a result of an impact by improperly protruding vehicle equipment, while ignoring the low-frequency vibrations produced by the passage of normal vehicles.

In a preferred embodiment, the transducers and their associated strike plate assemblies are mounted on the railroad ties by means of vibration-absorbing members, such as neoprene bodies or the like, so as to isolate the strike plates and transducers from the ordinary low-frequency vibrations produced in the rails and ties by a passing train.

Further, the transducer means of a signaling system in accordance with this invention are connected to a suitable electric circuit, whereby the electrical outputs of the transducers, upon vibration of the strike plates associated therewith, are utilized to actuate an indicator or alarm. In the preferred embodiment, the electrical circuit includes an audiofilter of high-pass characteristics, thus providing additional discrimination against the aforementioned low-frequency vibrations produced 'by the passage of heavy railroad vehicles.

In accordance with the preferred embodiment disclosed herein, the strike plate assemblies are mounted alongside the rails of a railroad track, both between and outside the rails. Thus, dragging vehicular equipment, whether between the rails or to the side thereof, will impinge upon the detector assemblies comprising the several strike plates and associated transducers.

Further, those portions of the strike plates between but adjacent the rails serve as loose-wheel detectors, since a flanged wheel which is loose on its axle may be displaced on its axle inwardly of the rail on which it is riding, resulting in an impact of the flange on such a Wheel with the adjacent strike plate.

In addition, the preferred embodiment of the present invention permits detection of excessive wheel tread wear, or cupped wheels, usually exhibited as high flanges on the internal wheel flanges, or in the production of a second, external flange. In either case, the worn tread per- 85 L. ASPINAL MEASUREMENTOF 'mz: GAS CONTENT OF METALS BY MASS SPECTROSCOPY P1199! arm, .17 1966 3 Sheets-Sheet 2 FIG. 2.

INVENTOR MICHAEL L ESLIE ASPINAL Dec. 8, 31970 M. L. ASPINAL 3,546,449

MEASUREMENT THE GAS CONTENT OF METALS BY MASS SPECTROSCOPY Filisd Jan. 17. 1966 Sheets-Sheet 5 mac/v mmms (Mme/v51, 8

PRESSLREC 0, '10 v in 3090 READNG OF SPECTROMETER OUTPUT RECORDER F163 7 KQTB L m5 (MINUTES) FIG.4 'INVENTOR V v MICHAEL LESLIE ASPINAL bW/dZYZETl United States Patent Office 3,546,449 Patented Dec. 8, 1970 US. Cl. 250--41.9 26 Claims ABSTRACT OF THE DISCLOSURE A method and apparatus for measuring the gas content of metals. An oven is provided in which a sample is melted under evacuated conditions to liberate gases. Liberated gases are conducted through a manifold system of variable volume into a mass spectrometer. The value of the mass charge ratio of a selected peak is monitored until a step-like rise in the magnitude of that peak takes place and the magnitude of that step-like rise is measured. The amount of the gaseous constituent present in the sample is determined from this measurement. The disclosure also includes an improved oven for melting a sample under evacuated conditions.

This invention relates to the measurement of the gas content of solids, and finds particular application in the measurement of the quantity of oxygen, nitrogen, or hydrogen in, say, copper.

One method by which the gas content in a solid, for example a metal, can be ascertained is to measure the gas released when a sample of the solid is melted under vacuum. The gases liberated from the solid sample are compressed to atmospheric pressure before being analysed, and the bottom limit in the measurement of oxygen in a one gram sample is about 20 parts per million (p.p.m.). Upon refinement of that method, by removing the analysing section operating at atmospheric pressure, and substituting an analysing section operating at low pressure (0.3-0.001 Hg), the bottom limit in the measurement of oxygen in a one gram sample can be lowered to p.p.m.

However, for specialized purposes it is necessary to reduce the gas contents of metals to even lower levels, for example copper for vacuum switch contacts should have an oxygen content of less than one part per million. During manufacture, it is necessary to test the metal to ensure that its degree of refinement is sufficiently great.

An object of the invention is to provide an improved method and apparatus for determining the gas content of a solid specimen.

A further object of the present invention is the propriate to a particular gaseous constituent of the released gas until a step-like rise in the magnitude of that peak takes place, measuring the magnitude of that step-like rise, and from the known characteristics of the apparatus interpreting that measurement as a measurement of the content of that gaseous constituent in the specimen.

Preferably the mass spectrometer is set to monitor continuously a single selected mass/charge ratio appropriate to the particular gaseous constituent.

Alternatively, the mass/charge ratio spectrum can be scanned, when all the gases have been liberated from the metal sample, to determine the peak heights, the time required for complete liberation being determined by the step like rise for mass/charge ratio 12 reverting to the normal blank rate (or rise) shown on a pen recorder.

In each case, some permanent record of the output of the mass spectrometer is preferably made automatically rather than by an operator.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic representation of apparatus for the measurement of the gas content of a metal specimen;

FIG. 2 is a sectional side elevation of a furnace section shown in FIG. 1;

FIG. 3 is a typical calibration curve for shown in FIGS. 1 and 2; and

FIG. 4 is a graphical representation of the output from a mass spectrometer shown in FIG. 1.

Referring first to FIG. 1, a furnace section 1 has its outlet duct 3 connected through an oil diffusion pump 5 to a cold trap 7, the outlet duct 8 of which is connectible through a three-way tap 9 alternatively to a manifold 11, to a further cold trap 13, or to both manifold 11 and cold trap 13. Tap 9 can be used instead to connect manifold 11 only to cold trap 13. The outlet from cold trap 13 is connected through a glass mercury diffusion pump 15 and a rotary vacuum pump 17 to an exhaust 19.

The manifold 11 is provided with a Pirani pressure gauge .21 effective to indicate pressure in the region of 100 microns of mercury. A McLeod gauge 23 is connected to the manifold 11 and is used in calibration of the apparatus. Bottles 25, 27 and 29, containing respectively carbon monoxide, nitrogen and hydrogen, all of very high purity, are connected to the manifold respectively through pairs of valves 25A and 25B, 27A and 27B, and 29A and 29B. Also connected to manifold 11, respectively through valves 31A, 33A and 35A. are three expansion chambers 31, 33 and 35, one or more of which can be utilised to increase the volume of a gas specimen contained in the manifold by a known amount and thus reduce its pressure to a convenient value. The gas sample inlet of an ion source chamber 41 of a mass spectrometer 43 is connected to the manifold 11 through a valve 45 and a capillary leak 47 made from precision bore capillary tubing and having a conductance of 1.7){10- litres per second. This gas sample inlet is also connected to the manifold through a valve 49 and a capillary leak 51 having a conductance of 0.5 1O litres per second.

The mass spectrometer 43 includes an evacuated chamber 55 subjected to a transverse magnetic field by a permanent magnet 57, which field is normal to the plane of FIG. 1. The ion source chamber 41 includes an electron gun (not detailed) which produces an electron beam used to bombard the geseous specimen and produce ionthe apparatus ized particles. The chamber also includes an accelerating electrode (not detailed) which projects the ionized particles as an ion beam 41A through the magnetic field. By interaction of the ions and the magnetic field, each ion follows a trajectory determined by its electric charge, its velocity (i.e. the accelerating voltage), its mass and the strength of the magnetic field. In a beam of ions travelling at equal velocities, the ions of different mass/ charge ratios will group to form a spectrum, and those ions having a selected mass/ charge ratio will pass through a narrow slit 59' to impact on a collector electrode 61. The electrical current from electrode 61 is thus an indication of the rate at which ions of the selected mass/ charge ratio are being received. Scanning of the spectrum can be effected by changing the accelerating voltage applied to the ions. The output from electrode 61 detected with an electrometer 62E is applied through an amplifier 62A to a recording device 63, which suitably can be a potentiometric recorder having a inch wide recording chart, and can include a meter 63M. The mass spectrometer 43 is evacuated through a cold trap 65 by an oil diffusion pump 67 and a rotary pump 69.

Referring now to FIG. 2, the furnace section 1 includes a vertically extending silica furnace tube 71 closed at its lower end and clamped at its upper end to a stainless steel manifold 73. Mounted inside the furnace tube 71 is a graphite crucible 75 provided at its upper end with a graphite funnel 77 formed along its side with a slot 79. The funnel 77 serves to support the graphite crucible 75 inside a silica crucible 81. The space between the silica and graphite crucibles is packed with graphite powder which has passed through a 100 mesh sieve. The top rim of the silica crucible is turned in so that there is the minimum of gap between the silica crucible and the graphite funnel. This prevents graphite powder being blown out of the crucible during evacuation or outgassing. The furnace tube 71 is sealed to the manifold 73 by means of a Viton O-ring 83 fitting into a tapered groove and compressed by means of a screwed ring 85.

A 3 kilowatt, 2 megacycles per second induction heating coil 87 encircles the part of the furnace tube 71 in which the crucibles are located. A top flange 73A of the manifold 73 has secured to it a glass dome 91 to which are fixed a first lateral sample arm 93 and a second lateral stopper operating arm 95. The sample arm 93 is provided with a vacuum lock 97 through which samples can be inserted into arm 93 without seriously affecting the vacuum in the apparatus. The samples used are in the form of one or more 4 millimetre cubes of the metal to be examined. A guide passage 101 extends downwardly into the manifold and the furnace tube and enables an operator to cause a metal sample to fall into the funnel 77 and thus into the graphite crucible 75. An optical fiat 101A formed at the upper end of the guide passage 101 enables, through a reflecting prism 103, an optical pyrometer 104 to be used to measure temperatures. The stopped operating arm has arranged in it an iron slug 105 connected by a fine molybdenum wire 107 to a graphite plug 109 for the funnel 77. By movement of the slug 105 along the arm 95, using a magnet (not shown) arranged outside the arm 95, the plug 109 can be raised and lowered as desired to uncover and to block the funnel 77.

In use of the apparatus described above, the tap 9 is set to connect the pumps and 17 with the manifold 11 but not the furnace section 1, valves 31A, 33A and A are opened, and these pumps operated, with all the other valves closed, to establish a suitable vacuum in the manifold and the expansion chambers 31, 33 and 35. The mass spectrometer is evacuated by the pumps 67 and 69. The graphite crucible 75 is placed in the silica crucible 81, the funnel 77 is fitted and the space between crucible 75 and crucible 81 is packed loosely with graphite powder. The silica crucible is then placed in its support in the furnace tube, which is then fitted to the manifold 73. Valves 31A, 33A and 35A are now closed, tap 9 turned to connect manifold 11 and the furnace section 1 with the pumps 15 and 17, and the furnace section evacuated. This evacuation necessarily takes place slowly to avoid the graphite powder being blown out of the crucible. When the Pirani gauge 21 shows that the pressure in the furnace section has fallen below 100 microns, the oil diffusion pump 5 is started up. The pressure in the furnace section then continues to fall until it reaches a few microns. Outgassing of the crucible is started by energisation of the induction heating coil 87, and is carried out by raising the temperature of the crucible in about ten steps within half-an-hour up to a maximum temperature of 2,100 C. The crucible is held at this temperature for about an hour.

It is necessary to calibrate the apparatus and to check the calibration about once a week in normal use, and this is crried out by adding a small quantity of gas from one of the bottles 25, 27 and 29 to the manifold 11. This is carried out, for example for bottle 25, by opening valve 25A with valve 25B closed, closing valve 25A, and then opening the valve 25B to allow the relatively small sample of the gas trapped between the two valves to enter the manifold. Thus carbon monoxide can be released from bottle 25 and the mass spectrometer used to measure the mass/charge ratio 14 peak and the mass/charge ratio 12 peak, while the pressure is measured by the Mc- Leod gauge 23. In this manner a graph is obtained similar to that shown in FIG. 3, in which the pressure of the carbon monoxide in microns is plotted against the output meter reading of the spectrometer. Similar graphs can be prepared for nitrogen and for the hydrogen using gas from bottle 27 or from bottle 29 and measuring the mass/charge ratio 14 and the mass/charge ratio 2 peaks respectively.

After calibration is completed, and after a delay sufficient for the gas added for calibration to be eliminated from the system, the actual testing or measuring operation can commence. The sample, in the form of a cube of 4 mm. side, has its surface cleaned mechanically and/ or chemically. The temperature of the crucible is allowed to fall to a temperature suitable to the metal to be tested. The tap 9 is then reset to connect the manifold 11 to the furnace section 1. It is convenient to add a series of samples through the vacuum lock 97 during the outgassing of the graphite crucible, and store them in arm 93. The samples are moved along the arm by an iron slug 94 as required, the slug being moved with a magnet from outside the apparatus, to fall through the guide passage 101. The plug 109 is then lowered, by movement of the slug 105, to close the top of the crucible 75 except for the slot 79. The sample melts, and the gases contained in it are released, at the low ambient pressure, and pass into the manifold 11. The pump 15 is isolated from the manifold at this stage, and the evolved gas flows through the system towards the mass spectrometer 43. The gas is evolved in a period of two to eight minutes, and the pressure in the manifold 11 is determined by the quantity of gas released and by the total volume by which it is contained. This volume can be increased, by opening one or more of the valves 31A, 33A, 35A, to produce a suitable pressure in the manifold. The spectrometer is set to tread the peak at mass 12 if the carbon monoxide present is to be measured, or at mass 14 if the nitrogen present is to be measured. The gas passes into the mas spectrometer through either the leak 47 or the leak 51 depending upon whether valve 45 or valve 49 is opened. The rate at which the gas passes through the selected leak is found to have no appreciable effect upon the total gas pressure in the manifold 11 over the period of the test. The electrical output from the mass spectrometer electrode 61 is recorded on the chart recorder 63.

The form that this record takes is indicated in FIG. 4. It is found that the chart on the recorder includes a low initial reading 121E due to the background in the mass spectrometer and manifold 11. When tap '9 is turned to connect the furnace section 1 to the manifold 11 a rise is obtained 121D which indicates the blank rate for the apparatus. The sample is added to-the crucible, and a rapid rise is observed 121C, the rate of rise returns to the blank rate when all the gas has been released from the sample indicated by 121B. When the rate of rise has returned to the blank rate 121B the spectrum can be examined for nitrogen and hydrogen and methane, before the gas is pumped away from the manifold -11 using pump 15 and 17, the operation being controlled 'by valve 9.

To interpret the results of the test, the vertical height H between the part 121B and a projection of the part 121D is measured. This height is applied to the horizontal ordinate of the calibration graph (see FIG. 3) and the vertical ordinate indicates the partial pressure produced in the manifold 11 by the gas involved. From a knowledge of the volume involved, the content of the specified gas in the known weight of metal represented by the specimen can be expressed as a percentage.

'By way of example, the calculation of the results can be carried out as follows, using a notation in which the number indicates the mass/charge ratio, the suffix S indicates the peak height for that ratio when the sample is being analysed and the suffix B indicates the peak height for that ratio when no sample is present:

(A) OXYGEN the partof the mass 12 contribution attributable to carbon monoxide formed by reaction of the oxygen of the sample with the graphite of the crucible.

This figure A can be converted to a pressure P of carbon monoxide in microns from the calibration graph, and then multiplied by a factor depending on the volume used to collect the gas, which provides an answer in millilitres at N.T.P. (normal temperature and pressure). Then:

P X factorX 0.0715 Wt. of sample percent 0 in the specimen by Weight (B) NITROGEN the part of the mass 14 contribution attributable to the nitrogen. This figure B can be converted to a pressure P of nitrogen in microns from the appropriate calibration graph, and as for oxygen used to find the amount of nitrogen in milliliters at N.T.P. Then:

P XfactorX 0.125 wt. of sample =percent N inthe specimen by weight (C) HYDROGEN (2 -2 =C=the part of the mass 2 peak contribution attributable to the hydrogen. This figure C can be converted to a pressure P of hydrogen in microns from the appropriate calibration graph, and as for oxygen used to find the amount of hydrogen in millilitres at N.T.P. Then:

PH faetor X 0.0089 wt. of sample =percent H in the specimen by Weight The method of assessing the gas content of a metal specimen set out above is much more rapid than other methods of comparable sensitivity. Thus a run of twelve different steel specimens can be analysed in eight hours, this including all the time required for out-gassing of the equipment, and this is considerably faster than known methods, which can require a whole day for preparation and outgassing before any analysis starts.

What I claim is:

1. A method of measuring the gas content of a solid specimen, comprising melting that specimen in an evacu ated space and thereby releasing gas content therefrom, feeding from the evacuated space through a very small leak a sample of the released gas to the ionizing chamber of a mass spectrometer, monitoring over a period of time the value of a selected mass/charge ratio peak appropriate to a particular gaseous constituent of the released gas until a step-like rise in the magnitude of that peak takes place, measuring the magnitude of that steplike rise, and from the known characteristics of the apparatus interpreting that measurement as a measurement of the content of that gaseous constituent in the specimen.

2. The method claimed in claim 1, wherein the mass spectrometer is set to monitor continuously a single selected mass/charge ratio appropriate to the particular gaseous constituent.

3. The method claimed in claim 1, wherein the mass/ charge ratio spectrum is scanned, when all the gases have been liberated from the metal sample, to determine the peak heights.

4. The method claimed in claim 1, wherein a permanent record of the output of the mass spectrometer is made automatically.

5. A method of measuring the gas content of a solid specimen, comprising melting that specimen in an evacuated space, transferring the liberated gases into an intermediate reservoir of selectable volume, feeding the gases into a mass spectrometer through a restrictive leak so proportioned that the pressure in the mass spectrometer remains substantially constant for the duration of the analysis, and identifying and measuring the individual component gases by the operation of the mass spectrometer.

6. The method claimed in claim 5, wherein gas concentrations of less than one part per million by weight are identified and measured.

7. The method claimed in claim 5, wherein the evolution of a selected gas is continuously monitored by preselection of the mass/charge ratio of the chosen gas in the mass spectrometer and the ion current so produced is recorded as a function of time or other suitable Nariables associated with the method.

8. The method claimed in claim 5, wherein the nitrogen content of the sample is directly identified and evaluated by preselection in the mass spectrometer.

9. Apparatus for measuring the gas content of a solid specimen comprising:

(a) furnace means for melting the specimen in an evacuated environment and then retaining a molten specimen in place as gases are liberated therefrom by the melting;

(b) means for transferring the liberated gases to an intermediate reservoir of selectable volume;

(c) a mass spectrometer; and

(d) a restrictive aperture connecting the reservoir to the mass spectrometer and through which the gases can be fed into said mass spectrometer, said aperture being so proportioned that the pressure in the mass spectrometer remains substantially constant for the duration of an analysis, whereby said mass spectrometer can be operated to identify and measure the individual component gases.

10. Apparatus as claimed in claim 9, wherein the means for melting the specimen comprises a crucible disposed within the evacuated environment and an induction heating coil disposed outside that environment.

11. Apparatus as claimed in claim 10, wherein the crucible is a graphite crucible and is supported in a silica crucible, the space between the silica and graphite crucibles being packed with a graphite powder.

12. Apparatus as claimed in claim 11, wherein a vac uum lock is provided through which specimens can be inserted into the evacuable environment Without destroying the vacuum therein.

13. Apparatus as claimed in claim 12, wherein the mass spectrometer has a plurality of ion collector electrodes, each with its own recording means, to allow simultaneous observation and measurement of a plurality of component gases.

14. Apparatus for measuring the gas content of a solid specimen, comprising:

(a) heating means for melting such specimen;

(b) crucible means for holding such specimen when in its molten state;

(0) means for containing the gases liberated from a specimen when it is melted;

(d) a mass spectrometer having an ionizing chamber;

(e) means for passing said liberated gases to said ionization chamber at a known rate; and

(f) means for monitoring the output of said mass spectrometer whereby said mass spectrometer can be operated to identify and measure the individual com ponents of the liberated gases.

15. Apparatus as claimed in claim 14 in which said means for transferring said gases to said ionization chamber at a known rate comprises a first container adapted to receive said gas from said means for containing said gases, means for measuring the gas pressure in said container, and a restrictive leak through which the gases in said container can be fed to said mass spectrometer, said restrictive leak being so proportioned that the pressure in the mass spectrometer remains substantially constant for the duration of an analysis.

16. Apparatus as claimed in claim 15 further comprising a second container adapted to contain a known gas and a valve connecting said second container to said first container.

17. In combination:

(a) a mass spectrometer including an ionization source adapted to produce a beam of ions, a collector for detecting ions, and an analyzer for passage of a beam of ions emitted by the source onto the collector;

(b) said mass spectrometer including structure establishing an evacuated ion path from the source through the analyzer to the collector;

(c) a vacuum pump connected to the spectrometer to evacuate said structure establishing an evacuated path between said source and said collector;

(d) a furnace section including a gas-tight chamber;

(e) a manifold connected to the gas-tight chamber of the furnace section;

(f) leak means connecting the manifold to the ion source;

(g) a crucible in the furnace section;

(h) gas conducting means connected to the furnace section for controlling the gas environment therein; and

(i) heating means positioned sufiiciently near said cru cible to heat a sample within the crucible and cause the sample to evolve gases for analysis by said mass spectrometer.

18. The combination of claim 17 wherein said furnace section further comprises a vacuum lock connected to said manifold for admitting samples and means to transfer such samples from said vacuum lock to said crucible.

19. The combination of claim 18 wherein said means for transferring samples comprises a generally horizontally disposed arm communicating with the vacuum 1062 and connected to said furnace section and a paramagnetic g Within said arm.

8 20. The combination of claim 17 wherein said furnace section further comprises a plug within said furnace section means for guiding samples admitted through the vacuum lock to said crucible, and means for moving the plug toward and away from the crucible.

21. The combination of claim 20 wherein said means for moving the plug comprises a generally horizontal arm, a paramagnetic slug within the arm, and a flexible member connecting the slug to the funnel.

22. The combination of claim 17 wherein the furnace section comprises:

(a) a generally vertically disposed portion and a connecting portion communicating with the vertical portion and connected by the manifold to the source of the mass spectrometer;

(b) said vertical portion including an opening near the lower end thereof;

(c) a generally tubular furnace member having an opening near its top and being otherwise imperforatc, the furnace member being positioned with its opening in communication with said vertical portion lower opening;

(d) clamping and sealing means connecting the furnace member to the connecting portion;

(e) a crucible within said furnace member;

(f) a heating element around said crucible and adapted to heat a sample in the crucible; and,

(g) sample supply means connected to said vertical portion and adapted to drop samples through said vertical portion into said crucible.

23. The combination of claim 22 wherein an expansion chamber is connected to the manifold and a valve is interposed between the expansion chamber and the manifold whereby to permit the expansion chamber to be evacuated with the manifold and the furnace section and to permit the expansion chamber to be selectively connected to the manifold when the device is in use to control the pressure in the manifold and in the connected mass spectrometer.

24. The combination of claim 23 wherein another pump is connected to the mass spectrometer for evacuating the mass spectrometer.

25. In combination:

(a) a mass spectrometer;

(b) a furnace section including means to melt a metal sample and means to hold a metal sample in its molten state;

(c) a manifold connecting the furnace section to the mass spectrometer;

(d) valve means for closing the manifold-to-mass spectrometer connection;

(e) a pump connected to the manifold by a valve and selectively communicating with the manifold for evacuating the manifold and furnace section prior to operation of the device; and,

(f) a leak between the valve means and the mass spectrometer.

26. The combination of claim 25 wherein the furnace section comprises:

(a) a generally vertically disposed portion and a connecting portion communicating with the vertical portion and connected by the manifold to the source of the mass spectrometer;

(b) said vertical portion including an opening near the lower end thereof;

(c) a generally tubular furnace member having an opening near its top and being otherwise imperforate, the furnace member being positioned with its opening in communication with said vertical portion lower opening;

(d) clamping and sealing means connecting the furnace member to the connecting portion;

(e) a crucible within said furnace member;

(f) a heating element around said crucible and adapted to heat a sample in the crucible; and

10 (g) sample supply means connected to said vertical 2,819,401 1/1958 Lawrence 250-41.9 portion and adapted to drop samples through said 3,105,147 9/1963 Weilbach et a] 25043.5 vertical portion into said crucible. 3,117,223 1/1964 Brunnee 25041.9 2,412,236 '12/1946 Washburn 250--41.9(3) References Cited 5 2,569,032 9/1951 Washburn 250-419(5) UNITED STATES PATENTS 3,068,402 12/1962 Redhead 32433 2,714,164 7/1955 Riggle et a1. 250-41.9 WALTER STOLWEIN, Primary mi 2,775,707 12/1'956 Benapel 250-41.95 A. L. BIRCH, Primary Examiner 

